FIG. 1 is selective view of a related art nuclear core shroud 10, useable in a nuclear reactor like a BWR. Core shroud 10 may be positioned in a downcomer annulus region 20, which is an annular space formed between shroud 10 and an inner wall of a reactor pressure vessel (not shown) that receives fluid coolant flow and directs it downward for entry at a bottom of core 30. Shroud 10 may be a cylindrical structure surrounding core 30 that partitions the reactor into these downward and upward coolant flows on opposite radial sides of shroud 10. One or more jet pump assemblies 40 may line annulus 20 and direct coolant flow in this manner.
After being directed downward past core shroud 10, coolant may then flow up through core 30 inside shroud 10. Core 30 is typically populated by several fuel assemblies (not shown) generating heat through nuclear fission during operation, and the coolant exiting core 30 may be quite energetic and potentially boiling. This energetic fluid flows up through and out of core 30 and shroud 10, potentially into steam separating and drying structures and ultimately to a turbine and generator that converts the energy from the steam flow into electricity. A top portion 15 of shroud 10 may terminate below such drying structures, and various core equipment may rest on or join to shroud 10 about top portion 15, which may be called a steam dam. One or more protrusions or obstacles 16, such as steam dam gussets, seismic pins, or lugs, may be aligned about top portion 15 of shroud 10 to support or join a shroud head (not shown), chimney, or drying structures.
During a reactor outage, such as a refueling outage or other maintenance period, the reactor vessel may be opened and inspected, and internal structures of vessel may be removed. During an outage, loading equipment such as a bridge and trolley above the reactor, and 20-30 feet above core 30 and shroud 10, may move and load new fuel assemblies in core 30. Similarly, worker platforms may be installed about partial perimeters of the vessel for handling tools and inspections about the reactor periphery. Visual inspections of shroud 10, core 30, and/or any other component can be accomplished with video or camera equipment operated from the bridge or other loading equipment above the reactor during this time.